Calling device



Oct. 18, 1938. QBERGFELL 2,133,469

CALLING DEVI C E Filed Sept. 5, 1936 INVENTOR. HERBERT F OBERGFELLATTORNEY.

Patented Oct. 18, 1938 UNITED STATES PATENT OFFICE to AssociatedElectric Laboratories,

Inc.,

Chicago, 11]., a corporation of Delaware Application September 5, 1936,Serial No. 99,547

7 Claims.

This invention relates to calling devices or impulse senders of the typecommonly employed in automatic telephone systems for establishingtelephone connectio' nsbetween telephone lines or for remote controlsystems of various types in which selective operations are to beperformed.

Calling devices as employed in automatic telephone systems areextensively used and are well known to the average telephone subscriber.

Their mechanical and electrical design has reached high stages ofperfection from the operating companies and the subscribers viewpoint.However, considerable objection has been voiced by the subscribersbecause of the fact that the is calling devices produce a louddistracting noise when they are being operated. This noise distracts theattention of the subscriber while he is dialling the digits of atelephone number, causing him to forget the number being dialled, andalso invades his privacy by calling the attention of nearby persons tothe fact that a telephone call is being made. Telephone operators whoare constantly operating their calling devices are subjected to acertain amount of nervous tension by 5 the constant clocking noiseproduced by their own or adjacent operators calling devices.

It is accordingly the object of this invention to provide an improvedcalling device in which the objectionable operating noise is greatlyreduced or practically eliminated without detracting from the electricaland mechanical eiiiciency of the calling device.

A further object of the invention is to provide a calling device ofstandard construction with means for rendering its operation noiselesswithout extensive changes or alterations to its various parts therebycheapening the cost of the same.

A calling device of the type applicable to the invention and which iswidely used is that disclosed in Patent 1,642,822, issued September 20,1927, to H. F. Obergfell. This calling device has a finger wheel platewhich is variably rotatable by the user in accordance with the differentdigits of a wanted subscriber's telephone number. The finger wheelcarries a plate upon which is mounted a pawl, and associated with thepawl is a ratchet wheel having a series of teeth around its periphery.As the finger wheel is rotated the pawl is rapidly rotated and passesover the teeth in succession, the number being dependent upon the digitdialled. Upon release of the finger wheel it returns to normal by meansof a spring and at a constant governor controlled speed. At thebeginning of the return movement the pawl drops in and engages theadjacent tooth of the ratchet wheel and thereby rotates the ratchetwheel at the same time with the return movement of the finger wheel. Theratchet wheel controls mechanism to operate the impulse transmittingsprings to set the automatic switches at the distant 5 switching centeror exchange.

As the foregoing calling device is operated in accordance with a digitthe pawl, as pointed out, passes over a plurality of teeth of theratchet wheel in succession and being urged by a spring 10 drops betweeneach pair of teeth and then rides up over the following tooth. Each timethe pawl drops between the teeth it produces a loud clicking noise whichis noticeably audible and extremely disagreeable, particularly when thefinger 15 wheel is rapidly rotated. In addition this results inconsiderable wear and tear on the pawl and ratchet mechanism itself.

The objects of the invention are attatned in accordance with the featureof the invention by 20 the provision of resilient means interposedbetween the pawl and ratchet mechanism of the calling device. Suchresilient means may take the form of an auxiliary rubber ratchet wheelattached to the main ratchet wheel to take up 25 and absorb the forceand shock of the pawl dropping between the teeth of the ratchet wheel oralternatively providing the pawl with a rubber nose. In each case thepawl subsequent to dropping between the ratchet wheel and engaging the30 adjacent tooth makes a metal-to-metal contact to positively rotatethe ratchet wheel, the rubber being only utilized to absorb the shock orimpact of the spring actuated pawl at the time it drops off the end of aratchet tooth.

-The invention will be pointed out in detail in the followingdescription together with the accompanying drawing in which:

Fig. 1 illustrates a front view of a calling device with a portion ofcertain of the parts cut away; Fig. 2 is an extended perspective view ofthe pawl and ratchet mechanism of Fig. 1; Fig. 3 is an enlarged rearview of the mechanism; while Figs. 4 and 5 are rear views of the pawland ratchet mechanisms illustrating modifications of that shown in Fig.1.

Referring now particularly to Fig. 1, the finger wheel dial 5 arrangedwith its finger holes above the number plate 6, has a centralopening'keyed to a raised hub portion 8 of the plate 9 and to 50 whichit is held by means of a screw threaded in the hole in the center of hub8. Manual rotation of the finger wheel 5 clockwise therefore alsoresults in the movement of plate 9. The finger wheel 5 is rotated untilthe finger stop I 55 is encountered whereupon it is released and thenrotates counter-clockwise under control of a tension spring attached toshaft I5 at a governor controlled speed (not shown). The return movementis limited by a projection on plate 9 striking the stop I3. The pawl Iis pivoted at II to the plate 9 and is normally urged against andbetween the teeth of ratchet wheel I4 by the coiled tension spring I2.As the finger wheel is rotated carrying the plate 9 and pawl I 0 withit, the ratchet wheel remains stationary and the pawl snaps over theends and between the ratchet wheel teeth. Upon the return movement ofthe finger wheel the pawl engages one of the teeth thereby carrying theratchet wheel I4 along with it and also rotating the gear wheel which isformed integral with the ratchet wheel. Gear wheel 20 operates theimpulsing mechanism (not shown). So far the above parts are constructedand operate in the same manner as in the aforementioned Obergfellpatent.

In order to eliminate the clicking noise produced as pointed out by theassociation of the pawl with the ratchet wheel teeth a resilientauxiliary ratchet wheel I I is interposed between them. This ratchet ispreferably constructed of synthetic rubber which resists excessive wearand is immune to corrosion due to the presence of lubricating oil on thedial mechanism. The auxiliary ratchet wheel I1 is formed in the shape ofa ring (Fig. 2) with the ratchet teeth on the outside and a pair ofoppositely spaced projections I8 on the inside which engage notches I9on the hub portion formed on the ratchet wheel I4. The two ratchetwheels are thereby held together and movement relative to each other isprevented. A fiber bearing washer I6 is interposed between the auxiliaryratchet wheel I! and the plate 9 carrying pawl III in order to lessenthe friction between these parts when the mechanism is operating.

Referring now particularly to Fig. 3 which shows an enlarged rear viewof the pawl and ratchet mechanism with the gear wheel 20 cut away, itwill be seen that the teeth of the auxiliary ratchet wheel I! areslightly wider along their sloping or back sides than the teeth of themetal ratchet wheel I4. The extreme outside edges and the faces of theteeth of both ratchet wheels, however, coincide with each other. Now asthe finger wheel 5 is rotated manually in the direction indicated by thearrow it carries the plate 9 along with it and this in turn moves thepawl Ill around the teeth of the ratchet wheels I4 and I! which atpresent remain stationary. The nose of pawl I0 rides on the slopingsurface of the first tooth of rubber ratchet wheel N, then slides alongthe outside surface of the teeth of both ratchets until it reaches theface of the teeth whereupon under the urging of spring I2 it snapsagainst the sloping side of the next tooth of rubber ratchet wheel IT.The. impact shock of the pawl snapping off the end of each tooth isabsorbed and cushioned by the resilient surface of the ratchet I'Ithereby positively eliminating the clicking noises as the pawl passesover successive teeth. After the finger wheel 5 is stopped and releasedthe operated mechanism returns under spring power as has been pointedout. The nose of pawl ll] engages the face of the tooth of ratchet wheelI4 that it is stopped at, and establishing contact therewith pulls theratchet wheel I4 along with it to perform its function of operating theimpulsing mechanism through the medium of gear wheel 20. From theforegoing it will be seen that the resilient ratchet teeth cushion thepawl as it passes over the teeth while when the pawl is actuallyperforming its work of pulling ratchet wheel I4 around it makes a directmetal contact with the face of the metal teeth. The pawl thereforecontacts with a portion of each ratchet wheel tooth and auxiliary wheeltooth. Wear on the nose of the pawl and obnoxious noises areconsequently obviated. The auxiliary ratchet wheel I! is not subject toexcessive friction or wear and will last indefinitely. The addition ofthis resilient ratchet to calling devices already in use may be readilyaccomplished by merely replacing the regular ratchet wheel I4 with onehaving the hub and notches I9 formed in it, or the regular ratchet maybe machined and altered to provide these changes. The auxiliary ratchetI! and washer I6 are then added resulting in a noiseless dial.

In the modification of Fig. 4 the nose of pawl 20' is provided with arubber inset 23 held in place in a slot in the pawl and by a rivet 22.Spring 2| attached to the rivet 22 on the end of pawl 29 exerts a pullon the pawl which is in line with the pawl pivot thereby rendering theaction of the pawl semi-floating; that is, the spring has a tendency tohold back on the pawl as it falls between the ratchet wheel teeth,thereby lessening its force as it snaps against the sloping sides of theteeth. The rubber nose 23 in addition cushions the impact of the pawland eliminates the clicking noise. The pawl 20' is made shorter so as toprovide an effective length for the pawl spring 2|.

In Fig. 5 a modification is shown in which the nose of pawl 24 isprovided merely with a rubber insert 25 which is held in place in anopening of the pawl by a pin or rivet 26. This rubber insert on the pawlas it passes over the ratchet teeth cushions the impact of the pawl andprevents the metallic contact between the sloping sides of the teeth andthe nose. of the pawl. When the pawl, however, moves the ratchet wheelit contacts its metal trigger edge with the metal face of the ratchetteeth. This modification illustrates probably the simplest and cheapestmanner in which the invention may be applied to existing callingdevices, it being merely necessary to change the pawls.

What is claimed is:

1. In a pawl and ratchet mechanism wherein the pawl is moved oversuccessive teeth of the ratchet wheel, means for eliminating theclicking noise comprising an auxiliary ratchet wheel having teeth largerthan the teeth of the first ratchet wheel for preventing engagementbetween the pawl and the back of the teeth of the first ratchet wheel.

2. In a pawl and ratchet mechanism wherein the pawl is moved acrosssuccessive teeth of the ratchet wheel and passes from one tooth to thenext, an auxiliary ratchet wheel having resilient teeth, each tooth ofthe auxiliary ratchet wheel being of greater area than each tooth of thefirst ratchet wheel and arranged in juxtaposition to the teeth of thefirst ratchet wheel for eliminating the clicking pawl noise.

3. In a pawl and ratchet mechanism, a pair of ratchet wheels, one ofsaid ratchet wheels having the sloping surface of its teeth arrangedslightly in advance of the sloping surface of the teeth of the otherratchet wheel, and means for operating said pawl so as to move firstover a portion of a tooth of one ratchet wheel and then over a portionof a tooth of both ratchet wheels.

4. In a pawl and ratchet mechanism, a pair of ratchet wheels arrangedside by side, one of said ratchet wheels having resilient teeth arrangedwith the back of the teeth in advance of the back of the teeth of theother ratchet wheel, the front face of the teeth of both ratchet wheelsbeing coincident, means for moving the pawl forward over the back of theteeth of only one of said ratchet wheels, and means for moving the pawlbackward and into engagement with the front face of a tooth of bothratchet wheels.

5. In a calling device having a pawl, a ratchet wheel having metalteeth, an auxiliary ratchet wheel having teeth formed of resilientmaterial, means cooperative with both of said ratchet wheels for holdingthem in locked relationship, means responsive to the operation of saidcalling device for rotating said pawl across successive ones of theteeth of both ratchet wheels, the resilient teeth preventing anyengagement of the pawl with the back of the metal teeth and thuseliminating the noise of the pawl as it drops between the metal teeth,and means for rotating said pawl backward in engagement with the face ofone of said metal teeth to rotate both of said ratchet wheels.

6. In a calling device, a pawl and ratchet mechanism, means for movingsaid pawl across the back surface of successive ones of said ratchetteeth, means for moving said pawl back again in engagement with the faceof one of said ratchet teeth to rotate the ratchet wheel, and resilientmeans attached to said pawl for preventing any engagement between thepawl and the back of the ratchet teeth thus eliminating the clickingnoise of the pawl as it is moves across the back surfaces of saidratchet teeth.

'7. In a calling device, a ratchet wheel, a pawl, means for moving thepawl backward over the ratchet wheel without moving the wheel and formoving it forward to engage a tooth to move the wheel, an element ofresilient material interposed between the pawl and the back of the teethof the ratchet wheel, said element having a surface parallel to the backof a tooth of the ratchet wheel and preventing the pawl from engagingany part of the back of a ratchet tooth while permitting directengagement of the pawl with the front face of a ratchet wheel.

HERBERT F. OBERGFELL.

